nested heirarchies as evidence against darwinian evolution

it's important to note that the mammalian eye is essentially "inside out" indicating two completey different evolutionary paths

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indeed -- even after evolving some hard parts, some invertebrates have secondarily lost their supportive structures. for instance, there's quite a good advantage that the octopus has in its soft-bodied flexibility. teuthids and octopodes in fact evolved from animals that sported hard shells. at least twice. catfish routinely come up on land for food or cross small land barriers to journey to other bodies of water, and they're more or less unrelated to the lobe-finnded fish that gave rise to tetrapods. i think it happened a couple of times in arthropoda too, but arthropod evolution never really tickled my fancy much.

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i'm half thinking about posting images of each and every cambrian phylum. their similarities are rather startling -- posts by randman make it seem like we're talking about whole bodyplans popping into existence in the cambrian explosion and nothing new has happened since.we're really talking about thirty three different kinds of worms. {edit: okay, not all of them are worms, but the vast majority of them are. look it up}it's just that it happens that the minor difference in the worms is the major dividing feature for the eventual populous of the various phyla. there is more difference between modern humans and the first chordate than there is between that chordate and the other phyla at the time. that is, afterall, what a nested hierarchy is. the defining features at the basic level snowball as you go down the tree.just for fun, here's a phylum with no known (or rather, no confirmed) cambrian relative. or for that matter, aquatic member: onychophora, the "velvet worms." it's suspected they're somewhere between annelids and arthropods. the oldest fossils are from the carboniferous period. though it's possible that the mysterious cambrian fossil hallucigenia is related.Edited by arachnophilia, : No reason given.Edited by arachnophilia, : No reason given.

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randman, if you will kindly re-read the post you responded to, i provided a link to a phylum of worm that does not have a definite cambrian relative. but that's honestly probably due to poor fossil record.and there's essentially nothing that's keeping the common ancestor of all those phyla from shooting off another phyla, except for the fact that it no longer exists. lots of new worms evolve today, they're just descendents of those initial branches of the tree. this is, afterall, what the theory of common ancestry is about -- you end up with nested heirarchies.no new phyla evolve today because the characteristics we arbitrarily define phyla on happened at this stage of evolution, in the precambrian. that's when the common "animal" ancestor speciated into different branches. really, the division between phyla at this level is the same as the division between daughter species of a recently speciated genus. that's the bit that creationists always seem to have trouble with: it's the same as that 1+1+1.... problem. it's only by stacking generations that we end up with a cladistic tree that demands different rankings like "phyla" or "species." the basic divisions are exactly the same. just like the last 1+1 in the series of countless 1's equals 2, so does the first.and in any case, i think you'll find the phyla in the other six kingdoms of life evolved at different times. just as a hypothetical, can you design a worm 30 different ways?

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on the superficial level, yes. linnean classification is based on heredity, partially as described through homologous features, but simply similar traits. notice how insects, bats, and birds have all evolved similar traits -- wings -- but they are not grouped together? for that to happen, the common ancestor of all animal phyla would have to have offspring. unfortunately, we are only left with its offspring in the form of the existing phyla.

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whoa whoa hey now. that's assuming hullucigenia is an onychophora. i thought the word was still out on that. made a post earlier on that.Edited by arachnophilia, : No reason given.

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rand, can you fix the links in this post? they're messing up the whole page.

something like this: Choanoflagellate - Wikipediaearly sponges are somewhat like colonies of these things. in other words, the common ancestor of all animals is a single-celled organism. animals came about based on ways of grouping and specializing those cells. no offense, but that's just kinda silly if you understand what common descent is. you're getting confused by the fancy names for various levels of clades. but one split is the same the next. you might as well be asking why you have no new grandfathers. similarly, two generations ago, your two grandfathers existed. but the "grandfather" energy must have run out, because that stage did not repeat. it's just that silly. "phylum" is an arbitrary stage in the hereditary grouping of the tree of life. just like "grandfather." why, if you have kids, your father is a "grandfather" and those kids have kids, you're a "grandfather." it's all arbitrary what we're calling what stage. ok, look. once again, we're talking about basically 30 some odd kinds of worms, some colonial corals and sponges, and whatever the hell you wanna call bryozoa.you're honestly calling the different between flatworms and roundworms more significant than the difference between mice and men? or for that matter, men and roundworms? i guess that's a judgement call there, but it's a strange one. i would easily say that life is far more diverse today than it was the cambrian. it's a snowball process -- change compounds. more speciation and more genetic divergence means more variety. period. i don't know why creationists have such problems with these relatively basic ideas of common sense. when you've shown a reasonable grasp of what the "darwinian evo model" is, please feel free to come back and make comments on it. but when you keep making comments about how evolution has run out of steam because common descent states that we will see nested heirarchies as opposed to continually occurring random offshoots and a cladographic mess, well.

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and we're still really only talking about animals. when did the plant and fungi phyla emerge? not to mention protista and monera (eubacteria and archaebacteria)?

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i'll do better. i'll name one that emerged during the cretaceous, only 125 some million years ago:magnoliophyta.the angiosperms, flowering plants, are an entire phylum (or "division" in botany) that has evolved quite recently, well after the cambrian animal explosion. i know people are more familiar with animals, but we're really limiting the discussion by ignoring the other kingdoms, which spread out at different rates and at different times.

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i'm not sure i would call plants "critters."

well, i think it's more that everyone is more familiar with animals. i think like 95% of the evolution discussion is over animals, and at least 70% of that over vertebrate animals. it's just what we relate to better, being vertebrate animals.but yeah, it just happens that animal phyla had its major explosion in the (pre)cambrian. nevermind that his logic doesn't make any sense, it's completely factually incorrect when we look at plants, fungi, protists, and monera.

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read it a little more closely. "major explosion" is not exclusive. i did not say that every animal phylum appeared in the cambrian or before. just that this time represents a period of a lot of speciation, and that more division appear here than at any other single point in history. i gave you one 125 mya.

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they're not. but it's a good example of phyla (possibly even kingdoms) evolving at other times. i'm not sure why you don't understand that this a refutation of your point -- you asked for phyla at other times, and you got them. instead, you'll keep insisting that new ancestors should arise randomly. i don't think you understand how common descent works.as for being ill-informed, i'll leave others to take your flamebait.

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yes. just to echo what mark said, let me use some terms you'll probably understand better:it's been 2500 years now, why are there no new tribes of israel? by religious standards, looks like god has stopped blessing people.now, if you can figure why that statement is nonsense, nonsequitor, and factually incorrect, then you'll figure out why your argument is also those things.

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